The long-term objective of this research is to establish ultrasound as a safe, effective, and non-invasive method for assessing fracture risk, an important component in clinical management of osteoporosis. Osteoporosis afflicts over 20 million people in the U.S., responsible for more than 275,000 hip fractures annually. Currently, the primary means for assessment relies on densitometric techniques. These methods subject the patient to ionizing radiation, are relatively expensive, and do not always provide good estimates of bone strength. Ultrasound offers several potential advantages. It is non-ionizing and relatively inexpensive. Moreover, since ultrasound is a mechanical wave and interacts with bone in a fundamentally different manner than electromagnetic radiation, it may be able to provide more accurate estimates of bone strength compared with current densitometric methods. The goal of this research is to significantly improve the effectiveness of current ultrasonic bone assessment techniques by demonstrating the feasibility of a new ultrasonic system to assess bone. The system employs a novel parametric signal processing approach which is ideally suited for analog and real-time implementation. Thus this research may enable less expensive and easier to use ultrasound devices, which are also less sensitive to various experimental artifacts. The specific aims are to measure a set of new ultrasonic parameters and compare them with presently used features, namely BUA and ultrasound velocity, in calcaneal bone samples. A comparison will be made of their respective capabilities to estimate bone density and bone strength. This comparison will include cost, ease of use, and accuracy and precision of the bone density and bone strength estimates. PROPOSED COMMERCIAL APPLICATION: Osteoporosis is a major health concern in the United States, afflicting over 20 million people, and whose incidence is increasing as the average age of the U.S. population increases. An effective, relatively inexpensive and safe technique such as ultrasound for assessing osteoporosis would be an extremely emportant benefit to the patient population, and represents an enormous commercial opportunity. Ultrasound's importance will grow as various new pharmacologic agents are approved for treatment, thus requiring periodic assessments of efficacy.